Serine protease inhibitors (serpins) regulate a multitude of physiological pathways, e.g. inflammation, coagulation, fibrinolysis, apoptosis and extracellular matrix remodeling. The reactive loop of a serpin is cleaved by the serine protease and the serine protease is inactivated via disruption of the catalytic site.
Alpha1-antitrypsin is a 394 amino acid, 52 kDa, glycoprotein synthesized by hepatocytes, macrophages and intestinal and bronchial epithelial cells. Crystal structures show that alpha1-antitrypsin is consisting of five beta-sheets, nine alpha-helices and an exposed mobile reactive loop comprising 14 residues that presents a peptide sequence as a pseudo-substrate for the target protease. Cleavage of the scissile reactive bond, denoted as P1-P1′ results in an irreversible conformational change wherein the N-terminal residue of the loop being completely incorporated into the middle of the beta-sheets of alpha1-antitrypsin as strand 4a (Schechter, I., and Berger, A., Biochem. Biophys. Res. Commun. 27 (1967) 157-162; Loebermann, H., et al., J. Mol. Biol. 177 (1984) 531-557; Baumann, U., et al., J. Mol. Biol. 218 (1991) 595-606; Baumann, U., et al., J. Mol. Biol. 226 (1992) 1207-1218; Mourey, L., et al., Biochim. 72 (1990) 599-608; Mourey, L., et al., J. Mol. Biol. 232 (1993) 223-241).
After proteolytic cleavage by its target protease, P1 Met and P1′ Ser are separated and the unprimed active site loop is inserted as strand 4a in the antiparallel beta-sheet A. A peptide with the amino acid sequence of strand 4a, residues 345-358 of human alpha1-antitrypsin Thr-Glu-Ala-Ala-Gly-Ala-Met-Phe-Leu-Glu-Ala-Ile-Val-Met, (Seq ID NO: 89),associates with intact alpha1-antitrypsin and forms a stoichiometric complex with properties similar to cleaved alpha1-antitrypsin (Schulze, A. J., et al., Eur. J. Biochem. 194 (1990) 51-56).
In WO 97/024453 receptor specific chimeric viral surface polypeptides for viral and particle incorporation and internalization in target cells are reported. A covalently attached complex of alpha1-antitrypsin-protease inhibitor with a water soluble polymer is reported in EP 0 147 761. In US 2006/0040867 inhibitors of serine protease activity and their use in methods and compositions for treatment of bacterial infections are reported.
Schule, A. J., et al., report structural transition of alpha1-antitrypsin by a peptide sequentially similar to beta-strand S4A (Eur. J. Biochem. 194 (1990) 51-56). Multifunctional anti-HIV agents based on amino acid sequences present in serpin C-terminal peptides are reported by Congote, L. F., in Anti-infective agents in medicinal chemistry, Bentham Science publishers, Hilversum (NL), 7 (2008) 126-133. Qi, Z., et al. (J. Biol. Chem. 283 (2008) 30376-30384) report rationally-designed anti-HIV peptides containing multifunctional domains as molecule probes for studying the mechanism of action of the first and second generation HIV fusion inhibitors. Methods and compositions for inhibition of membrane fusion-associated events, including HIV transmission, are reported in WO 01/51673. In WO 02/063017 integrin-binding chimeras are reported. Heparin fragments and fractions with anti-HIV action are reported in EP 0 355 905. In WO 00/52034 and U.S. Pat. No. 6,849,605 inhibitors of serine protease activity, methods and compositions for treatment of viral infections are reported.